Standing in a brown suit, his shaggy hair combed back from his dark-rimmed glasses, Bruce May quietly told a Howard County District courtroom that he “wasn’t thinking, just acting,” when he shot marbles at a mobile speed camera.

The 50-year-old Ellicott City man on Wednesday pleaded guilty to reckless endangerment and destruction of property less than $500, after using a slingshot to shoot marbles at the van with the camera and a Howard County auxiliary police officer sitting inside.

“I honestly did not think anyone was in the van,” Mr. May said. “What I did was very, very stupid.”

Mr. May was arrested on June 26, according to charging documents filed in court, after auxiliary officerPieter Lucas caught him slinging marbles at his van, which was parked along U.S. Route 144 near Manor Woods Elementary School.

Mr. May’s attorney said his client was having a bad day and his anger got the best of him. A district judge said that was no excuse.

“Doing what you did is wrong,” Judge Mary C. Reese said. “You’re taking out your anger the wrong way.”

Mr. May’s attorney, John Moody, told the courtroom his client was frustrated the day he came across the speed camera, not only from mounting stress about work problems, but because he’d been caught twice in the previous six weeks for speeding.

“He’s not a criminal, not a scofflaw,” Mr. Moody told Judge Reese. “He’s an Ellicott City boy all his life, and he was just having a bad day.”

That bad day, however, ended up costing Mr. May more than $450 in restitution for vehicle damage, 40 hours of community service and an order to enroll in an anger management course — which Mr. Moody said he is already taking.

According to charging documents, Mr. Lucas was in the van monitoring cars in a posted 40 mph speed zone at about 5 p.m. June 26. Then he heard “a loud thud and an unknown object strike the side of the van.”

He watched a gray minivan pass by. Over the course of the next few minutes, he watched it pass two more times, the final pass being when Mr. Lucas saw Mr. May “with a slingshot fire an object at the van.”

Mr. Lucas followed the minivan and pulled Mr. May over. He told the officer what he was doing and handed him the slingshot. The report states Mr. May told officers “he was sorry and he was stupid for shooting at the van.”

In court Wednesday, Mr. Lucas said he was simply “trying to do my job without getting injured.”

The Howard County speed camera program is less than a year old and consists of two mobile cameras transported in vans.

Mr. May’s attack was not the first the area has seen on speed cameras.

Earlier in June, a Maryland State Highway Administration speed camera van in Ellicott City was damaged by someone who threw a rock through its window. The operator of that van was also injured. One day later, a back window of a county camera van parked nearWaverly Elementary School — about six miles away —was broken by an unidentified projectile.

Last year, a man wielding a shotgun and hammer smashed the windshield of a car with a mounted speed camera parked along Route 295 near Baltimore/Washington International Thurgood Marshall Airport.

Fred Von Briesen, the speed enforcement program administrator for Howard County, said passers-by harass camera operators “on a routine basis,” whether its screaming or throwing water bottles at them.

After hearing the judge’s verdict, he said he hoped Mr. May’s story would “get people to think twice” before trying the same thing.